There are known a variety of processes for the preparation of deionized and deaerated water which include processes using an ion-exchange resin column, a decarbonator, a vacuum deaerator including vacuum deaerators of the membrane type, and a deoxygenating agent. Also known are various apparatus for use with those known processes.
As conventional processes for preparing deionized and deaerated water to be employed as boiler water, there is known technology involving the use of an ion-exchange resin for deionization and use of a deoxygenating agent for deaeration, technology involving the use of an ion-exchange resin for deionization and the use of a heating deaerator, and technology involving the use of a reverse osmosis membrane for deionization and the employment of a vacuum deaerator of a membrane type for deaeration. The technology using the ion-exchange resin and the deoxygenating agent presents problems of achieving a sufficient degree of deaeration, the requirement of a boiler compound, and the fact that this process requires multiple steps. The technology involving the employment of the ion-exchange resin and the heating deaerator suffers from the difficulties that it requires the use of a boiler compound as well as high temperatures and high pressures, thereby making the instrument large in size. Further, the technology using a vacuum deaerator has the problem that a high-pressure pump for feeding a liquid is required for the reverse osmosis membrane.
Further, as conventional processes for the preparation of deionized and deaerated water, there are known processes using an ion-exchange resin and a reverse osmosis membrane for deionization and a vacuum deaerator for deaeration. These processes, however, suffer from the difficulty that an apparatus of large size is required in both cases.
As described above, the conventional processes and apparatus for use with those processes have problems such as performing deaeration to a less sufficient extent or requiring an apparatus of a size larger than necessary because they are each a continuous combination of individual steps.